Conventional phase shifters are often used in phased-array RF systems to provide controllable phase shift of RF signals. There are various types of phase shifters, including liquid crystal phase shifters. Prior developments in the field of liquid crystal phase shifters are disclosed in Dolfi et al. (U.S. Pat. No. 5,936,484), which is incorporated herein by reference in its entirety. Dolfi et al. discloses a conventional liquid crystal phase shifter that provides a tunable phase shift for use in a phased-array. The conventional phase shifter in Dolfi et al. is constructed in a microstrip configuration, in which the signal line is formed on an insulating substrate and a liquid crystal layer separates the signal line and a ground plane.
In the conventional liquid crystal phase shifter disclosed in Dolfi et al., an electric field (produced by the DC bias between the signal line and the ground plane) rotates the orientation of the liquid crystal molecules, creating a change in dielectric permittivity of the liquid crystal as seen by the propagating RF signal and, ultimately, a change in the propagation velocity of the RF signal along the phase shifter. Accordingly, the change in the propagation velocity appears as an electric phase shift for small RF device lengths. The amount of phase shift is proportional to the applied voltage and electric field. Accordingly, the amount of phase shift returns to its base value when the voltage is removed.
However, one of the disadvantages of conventional liquid crystal phase shifters is the limited amount of phase shift produced per applied voltage, typically on the order of half that of nanoparticle-enhanced liquid crystal phase shifters. In consequence, in order to produce a given amount of phase shift, conventional phase shifters require increased RF device size on the order of double that of similar nanoparticle-enhanced liquid crystal phase shifters.